The present invention relates generally to methods of and apparatus for reinforcing mine roofs, and more particularly, toward a method of and apparatus for feeding and inserting roof bolts into resin filled holes preformed in the roof.
Mine roof failures are often caused by the natural tendency of rock strata to flow into the void created by removal of coal. As the flow occurs, it creates a separation of the various levels of rock strata, contributing to failure or collapse of the roof, thereby jeopardizing the lives of personnel working in the underground mine.
The purpose of the rock bolt support system is to resist strata movement in order to provide safer working conditions. The rock bolt supporting system of the prior art uses elongated roof bolts usually a few feet in length which are inserted into openings drilled in the strata above the roof of a mine passageway at predetermined, spaced apart intervals. The bolts conventionally include some type of anchor-like fastening means at one end adjacent the uppermost part of the hole, and a stop at the opposite end of the bolt to place the bolt under tension. By this arrangement, the strata above the roof are compressed in a vertical direction to bind together thinly banded rock layers.
The effectiveness of these bolts depends on the tension applied between the bolt head and the anchored end. The bolt must also penetrate sufficient strata in order to achieve reliable anchorage; if the anchor is located in soft areas of strata above the roof, the anchor slips and the roof sags or bulges in the area between the bolts.
A recently developed system for reinforcing mine roofs involves anchoring the roof bolts in resin filled holes formed in the roof. The resin anchors the entire length of the roof bolt to surrounding strata. As a result, the system does not depend solely on rock strata for anchorage, because the resin forms a bond between the bolt and all of the surrounding rock strata. Since the bolt is not limited to anchorage at a single point, there is no requirement for single point anchorage between the opposite ends of the bolt. Further, the unification of the resin, bolt and strata provides the necessary strength and rigidity to prevent sag by acting as a reinforcement which anchors the individual stratified layers of rock into a single, high strength beam.
Heretofore, the resin filled bolt system has been installed by drilling spaced apart holes into the roof and filling the holes with resin. Then, at each hole, the full length of a unitary, premanufactured roof bolt is inserted and held momentarily in place as the resin sets.
The application of individual roof bolts into the resin filled holes has been found to be undesirably time consuming. It is necessary to apply the roof bolts to the resin filled holes as quickly as possible in order to (1) increase production rates, and (2) minimize shifting in rock strata after the holes have been drilled but before bolts have been applied. In a resin anchored bolt system, there presently exists a need for a method of and apparatus for rapidly inserting roof bolts into resin filled holes preformed in the mine roof.
Accordingly, one object of the present invention is to provide a new and improved method and apparatus for reinforcing mine roofs.
Another object is to provide a new and improved method of and apparatus for feeding roof bolts into resin filled holes preformed in a mine roof.
Another object is to provide a new and improved method of and apparatus for rapidly feeding and inserting roof bolts into resin filled holes in a mine roof.
Yet another object is to provide a new and improved method of and apparatus for reinforcing a mine roof, wherein handling of individual roof bolts is not required.